Anomalous optical and electronic properties of dense sodium

Based on the density functional theory, we systematically study the optical and electronic properties of the insulating dense sodium phase (Na-hp4) reported recently (Ma et al., 2009). The structure is found optically anisotropic. Through Bader analysis, we conclude that ionicity exists in the structure and becomes stronger with increasing pressure.

Upconversion emission of a Er3+-doped glass microsphere under 633 nm excitation

In this work, The TBS glass microspheres doped with Er3+ for morphology-dependent resonances of upconversion emission were designed. The glass sample components are 25TiO(2)-27BaCO(3)-8Ba(NO3)(2)-6ZnO(2)-9CaCO(3)-5H(3)BO(3)-10SiO(2)-7water glass-3Er(2)O(3) (wt%), and the emission spectra of TBS glass and a TBS glass microsphere (about 48 mum in diameter) were measured under 633 nm excitation and discussed. The strong morphology-dependent resonances of upconversion luminescences in the microsphere were observed. The observed resonances could be assigned by using the well-known Lorenz-Mie Formalism. (C) 2003 Elsevier Ltd. All rights reserved.

Lasing of CdSSe quantum dots in glass spherical microcavity

Glass spherical microcavities containing CdSSe semiconductor quantum dots (QDs) of a few microns in diameter are fabricated using a physical method. When a single glass microspherical cavity is excited by a laser beam at room temperature, very strong and sharp whispering gallery modes are shown on the background of PL spectra of CdSSe QDs, which confirms that coupling between the optical emission of embedded QDs and spherical cavity modes is realized. For a glass microsphere only 4.6 mum in diameter, it was found that the energy separation is nearly up to 26 nm both for TE and TM modes. With the increasing excitation intensity, the excitation intensity dependence of the emission intensity is not linear in the double-logarithmic scale. Above the threshold value, the linewidths of resonance modes become narrower. The lasing behavior is achieved at relatively low excitation intensity at room temperature. High optical stability and low threshold value make this optical system promising in visible microlaser applications. (C) 2002 Elsevier Science B.V. All rights reserved.